Flowable materials are commonly dispensed from pressurized containers. In many such containers, a gaseous propellent is mixed with the flowable material product, thus providing the motive force to expel the product from the container. One example of such a container is an aerosol can in which a propellant gas is provided to drive a liquid or an atomized gas-liquid mixture product from the container. In such containers, the initial pressure within the container often declines as the product is dispensed.
Although this type of pressurization system works adequately with some products, in many applications it is undesirable to mix the propellant gas with the product being dispensed. Such mixing may result in undesirable reactions between the product and the propellant, thus leading to a degradation of the product.
It is also undesirable to dispense many products with a declining pressure dispensing system. This is particularly true with carbonated liquid products, such as beer. It has been found that successfully dispensing carbonated liquids depends, in part, upon maintaining a predetermined relatively constant pressure differential between the inside of the container and the ambient environment. In a declining pressure dispensing system, this is generally not possible.
To overcome the problems discussed above, one pressurization system has been developed in which an expansible pressure pouch is placed within the product container. The pressure pouch includes a plurality of chemicals contained in a series of compartments within the pouch. When mixed together, the chemicals in the pouch generate gas and pressure, thus expanding the pouch and providing pressure to drive the product from the container. As product is dispensed from the container, the pouch expands, causing more compartments to open. This, in turn, causes the introduction and mixing of more gas-generating chemicals and, thus, the development of more pressure within the container. The expansible pouch, thus provides the dual functions of separating the propellant gas from the product and of maintaining a relatively constant pressure profile within the container.
Expansible pressure pouches may be formed by juxtaposing two sheets of flexible plastic material. The pouch compartments discussed above may be formed by releasably attaching one sheet to the other at selected seam locations, e.g., via a heat sealing technique. As the pouch expands, each releasable seam may be opened or peeled in a sequential manner to release more gas-generating chemical in a manner as described above. Examples of such expansible pressure pouches using peelable seam technology are disclosed in U.S. Pat. No. 4,785,972 to LeFevre; U.S. Pat. No. 4,919,310 to Young et al.; U.S. Pat. No. 4,923,095 to Dorfman et al. and U.S. Pat. No. 5,333,763 to Lane et al., which are all hereby specifically incorporated by reference for all that is disclosed therein.
As an alternative to peelable seams, the compartments of some pressure pouches are separated by frangible wall portions which fail or tear in response to increasing volume of an adjacent compartment. Examples of pressure pouches using such frangible divider wall portions are disclosed in U.S. Pat. No. 5,769,282 to Lane et al. which is hereby specifically incorporated by reference for all that is disclosed therein.
During typical operation of a pressure pouch dispensing system, the pressure pouch is first inserted into a dispensing container which is adapted to contain a flowable material product to be dispensed. After the container is sealed, the pouch is activated, thus applying pressure to the product in the container. This pressure is used to force product from the container when it is desired to dispense product from the container. As product is dispensed from the container, the pouch continues to expand.
As can be appreciated, in order to completely expend all of the product from the container, the pouch must fully expand such that it contacts the entire interior of the container. This is readily achievable in cases where the ends of the container are substantially curved, as in containers disclosed, for example, in U.S. Pat. Nos. 4,785,972; 4,919,310; 4,923,095 and 5,333,763, previously referenced. It has been found, however, that the use of pressure pouches, as described above, is problematic in containers having irregular, e.g., non curved, end portions. Specifically, it has been found that a pressure pouch will often fail to conform to the interior of a container in a non-curved area and a gap, thus, will be created between the pouch and the container wall. The product contained in this gap, thus, cannot be dispensed from the container. In some cases, the inability of the pouch to conform to the interior of the container will also cause the pouch to rupture, thus releasing the gas generating chemicals into the product to be dispensed in an undesirable manner. In either case, a portion of the product within the container cannot be dispensed due to the inability of the pouch to conform to the interior of the container.
This situation has sometimes been addressed in the past by providing a pouch having dimensions larger than that of the product container. In this manner, the pouch contains extra material which can unfold into the otherwise inaccessible areas of the container. This solution, however, has also been found to be problematic. Specifically, it has been found that, in many cases, the extra material of the larger pouch fails to unfold and, instead, becomes trapped by the expanding pouch itself. Accordingly, the larger pouch often fails to unfold and enter the inaccessible areas. Further, in order to insert such a larger pouch into a container, the larger pouch must generally be folded more times than a smaller pouch. Folds in a pressure pouch tend to be problematic in that they sometimes prevent or interfere with the proper mixing of the reactive components within the pouch. Accordingly, the fact that a larger pouch requires more folds than a smaller pouch tends to add to the problems associated with larger pouches. In addition, larger pouches tend to be more expensive to manufacture due to the increased material contained therein.
Thus, it would be generally desirable to provide an apparatus and method which overcomes these problems associated with flowable product dispensing pressure pouches.